New blog post! Part 6 of my “Haskell for Elm developers” series tackles the Foldable typeclass — how foldMap alone gives you foldr, length, sum, toList, elem and more for free, implementing it for a custom Tree in just 3 lines (or zero with DeriveFoldable!). Also covers scanl from Data.List.NonEmpty and the deep Foldable + Monoid connection via foldMap. Next up: Traversable!
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